Sticking cotton treatment method

ABSTRACT

The present invention relates to a method for treating sticky cotton aimed at reducing the stickiness of thereby treated cotton fibers. Said method comprises the following steps: a. sowing said cotton fibers with bacteria, by spraying, preferably by uniformly spraying an aqueous suspension of said bacteria, so as to achieve a maximum resulting humidity thereof of 16%; b. storing the thereby treated cotton fibers as a compressed bale; c. letting the sown bacteria act at notably room temperature for at least about one week.

The present invention relates to a method for treating sticky cotton aimed to reducing the stickiness of thereby treated cotton fibers. More particularly, the invention relates to treating sticky cotton by applying bacteria.

Cotton is one of the most used raw materials of the textile industry. World production of cotton fibers is estimated to be about 20 million tons per annum. About 20% of the produced cotton, approximately amounting to 4 million tons per year, is contaminated by sugars forming what is called sticky cotton. The cotton fibers may be polluted by insect honeydews, which are sugared excreta secreted notably by two polyphage homopter insects, an aphid (Aphis gossypii) and a white fly (Bemisia tabaci).

Sticky cotton causes significant problems during the different steps for producing and treating cotton fiber in the textile industry. Stickiness of cotton has a detrimental effect on the preparation and spinning method. Indeed, the presence of honeydews hinders proper operation of the preparation machines: bale breakers, carding machines, . . . which may lead to mechanical jamming of the latter requiring that a complete cleaning be carried out. Also, the stickiness from the sugars of honeydews causes windings of cotton fibers at the drawing units (straps, cylinders, . . . ) both at the speed frame and at the spinning frame, causing breakages of rovings or yams as well as a degradation of the quality of the obtained yam (increase in the number of neps and other irregularities).

Many solutions have been proposed for reducing the stickiness of cotton.

In industrialized countries, notably in the United States, cotton producers try to control the potential source of stickiness by treating cotton cultures with pesticides. This solution gives satisfaction only partly: the obtained results depend on the number of treatments which are carried out, on the date of the last treatment before harvesting, on the difficulty of attaining the insects localized on the lower face of the foliage. Furthermore, this solution is severely harmful to the environment.

Another approach consists of finding a remedy to the problem of stickiness by treating cotton fibers after harvesting. Many treatment methods are known along these lines:

-   -   heat treatment of cotton fibers, by document EP 196449;     -   mechanical treatment of cotton fibers, by document U.S. Pat. No.         5,153,968;     -   thermo-mechanical treatment of cotton fibers, by document EP         344631;     -   electromagnetic treatment of cotton fibers, by document EP         350669;     -   enzymatic treatment of cotton fibers by document EP 622487.

Document EP 622487 describes an enzymatic treatment of sticky cotton with a composition comprising at least one enzyme selected from the group: transglucosidase, pectinase, α-galactosidase, these enzymes being derived from the Aspergillus fungus. The treatment method for reducing the stickiness of cotton consists of applying said enzymatic composition onto the cotton fibers, before (by spraying a solution of said enzymes) and/or after harvesting (by soaking them in a bath containing a 4% solution of said enzymes).

Such a treatment of sticky cotton fibres, notably in its <<post-harvesting alternative>>, seems difficult to apply to industrial amounts of cotton. Moreover, spraying of enzymes before harvesting should necessarily be accompanied by sustained irrigation of cotton fields, because these enzymes need water to act on their substrates (carbohydrates present on the cotton fibers). Finally, generalized use cannot be contemplated with the high cost price of the enzymes used by this method for treating sticky cotton.

The present invention proposes to overcome the drawbacks due to the known methods for treating sticky cotton.

The object of the invention is to propose a biotechnological treatment method aimed to reducing the stickiness of cotton, this method is simple to apply, not very costly, without any negative impact on the environment and may be used for treating large amounts of cotton after harvesting on an industrial scale.

According to a first aspect, the invention relates to a method for treating a batch of sticky cotton fibers, intended to reduce the stickiness of said fibers, characterized in that it comprises the following steps:

-   -   a. sowing said cotton fibers with bacteria, by spraying,         preferably by uniformly spraying an aqueous suspension of said         bacteria, so as to achieve a maximum resulting humidity thereof         of 16%;     -   b. storing the thereby treated cotton fibers as a compressed         bale;     -   c. letting the sown bacteria notably act at room temperature for         at least about one week.

By <<resulting humidity>>, is meant the natural water regain of the cotton bale (about 8%) to which is added the humidity percentage (i.e. by taking into account water losses during the spraying treatment) actually provided by the cotton fiber treatment according to the invention.

The storage conditions in terms of duration and storage are determined in order to achieve the desired result, i.e., degradation of the sugars imparting stickiness to the cotton. This result is achieved within one week for room temperature storage, at between 15 and 20° C., but it may be achieved within a longer or possibly shorter time depending on local weather conditions.

In a preferred alternative embodiment, the resulting humidity inside the bale treated according to the method of the invention is between 8 and 13%. The aqueous suspension of bacteria comprises at least 10⁶ units forming bacteria colonies per ml of water. The concentration of the bacteria sown inside said bale is at least 10⁵ colony-forming units per gram of treated cotton.

The aqueous suspension applied in the method for treating sticky cotton comprises bacteria selected from: Lactobacillus, Pediococcus, Bifidobacterium, Lactococcus, Leuconostoc, Enterococcus and Streptococcus. In a characterizing way, these bacteria are capable of metabolizing the sugars notably present in the insect honeydews found on the cotton fibers to be treated. According to one embodiment of the invention, the aqueous suspension comprises bacteria selected from the group: Lactobacillus plantarum and Lactobacillus casei rhamnosus. Preferably, said aqueous suspension comprises bacteria selected from the Lactobacillus casei rhamnosus R0011 and Lactobacillus plantarum R1012 strains.

According to a second aspect, the invention relates to a freeze-dried powder containing the aforementioned bacteria, a powder which just needs to be dissolved in water in order to obtain the suspension to be sprayed.

According to a third aspect, the invention relates to a bag containing a determined amount x of said freeze-dried powder used for sowing an amount y of sticky cotton therewith.

The invention will now be described in detail.

The present application relates to a method for treating sticky cotton which aims to reducing the stickiness of cotton fibers, and, through this, optimizing the processability of the thereby treated cotton fibers. By cotton processability, is meant the capability of the cotton fibers of undergoing egrenation, carding, spinning, dying, weaving operations for obtaining quality cotton yarns/fibers/fabrics.

The method for treating sticky cotton according to the invention is applied to harvested cotton, either during the egrenation operation before actually baling it, or subsequently (for example at the spinning stage), with, in this case, the need to open the cotton bales which have been pressed earlier.

The method for treating sticky cotton fibers, intended to reduce the stickiness of said fibers comprises the following steps:

-   -   a. sowing the cotton fibers with bacteria by spraying,         preferably uniform spraying, of an aqueous suspension of said         bacteria so as to obtain a maximum humidity thereof of 16%;     -   b. storing the cotton fibers as a compressed bale;     -   c. letting the sown bacteria act notably at room temperature for         at least about one week.

In one embodiment, the treatment method according to the invention is applied to bales having undergone the pressing operation. In this case, the bale to be treated containing sticky cotton is first opened by means of a bale breaker, in order to form thin layers of fibers. In another alternative embodiment, the treatment method is applied to cotton bales just before they are pressed, this solution being particularly interesting for production areas affected by the sticking phenomenon.

An aqueous suspension of bacteria is sown onto the sticky cotton fibers of said bale by spraying, preferably by uniform spraying. Spraying may be carried out by hand or by means of a suitable spraying facility.

Preliminary tests carried out by the applicants have shown that certain bacteria, notably those selected from the group of Lactobacillus, Pediococcus, Bifidobacterium, Lactococcus, Leuconostoc, Enterococcus and Streptococcus are capable of metabolizing carbohydrates present on the sticky cotton fibers, carbohydrates which comprise the natural physiological sugars of cotton (glucose, fructose, saccharose) and insect honeydews. The main sugars contained in the honeydews are trehalulose, melezitose, saccharose, fructose and glucose. The bale sown as described is then closed and compressed. If necessary, the plastic or cotton envelope of the treated bale is sealed, so as to create an environment isolated from external conditions, in order to maintain constant humidity inside said bale. The bacteria are left to act at room temperature for at least one week.

The higher the humidity inside the bale, the larger is the metabolic activity of the sown bacteria, and the faster is the reduction in the stickiness of the thereby treated cotton fibers. The resulting humidity inside the sown bale should however not exceed 16%, in order to prevent occurrence of molds. It has been noticed that in the case of dried cotton before the treatment according to the invention, activity of the sown bacteria is reduced.

In a preferred alternative embodiment, the resulting humidity inside the bale is less than 13%, preferably between 8 and 11%.

The bacterial treatment of sticky cotton fibers according to the invention does not affect the degree of polymerization of the cellulose entering into the composition of the cotton fiber.

The invention will be better understood upon reading the following non-limiting exemplary embodiments.

EXAMPLE 1 Digestion of Carbohydrates Present on the Sticky Cotton Fibers, by Bacteria

Twenty four strains of bacteria from the LALLEMAND collection were submitted to a test of the use of sugars according to the API50CHL method (BIOMERIEUX). With this test, it is possible to demonstrate the capability of a given strain of using various sugars and polysaccharides. The tested strains belong to the Lactobacillus, Pediococcus, Bifidobacterium, Lactococcus, Leuconostoc, Enterococcus and Streptococcus genera.

Among the tested strains, only those using at least two of the following sugars: saccharose, trehalose and melezitose, i.e. nine strains, were submitted to a growth test in a MRS culture medium, where glucose was either replaced with saccharose or with trehalose, or with melezitose. The growth rate on these media was estimated by measuring the turbidity or optical. density versus time for twenty four hours of incubation at 30° C. Both strains having shown the best growth under these conditions: Lactobacillus casei rhamnosus R0011 and Lactobacillus plantarum R1012, were retained for tests of application on cotton fibers.

Both of these strains were deposited at the CNCM (Collection Nationale de Cultures de Microorganismes) (National Collection of Microorganism Cultures)) under the following numbers:

-   -   Lactobacillus casei rhamnosus R0011: CNCM I-1720;     -   Lactobacillus plantarum R1012: CNCM MA-18/50.

As known, these bacteria are not pathogenic.

EXAMPLE 2 Application of the Method for Treating Sticky Cotton Fibers, on a Laboratory Scale

Micro-bales of 50 g were used for investigating the effect of the bacterial treatment on the sticky cotton. The micro-bales have the same density as bales of standard dimensions. Preliminary tests had the goal of determining, in a first phase, the best way for sowing and moisturizing the micro-bales. Two sowing methods were tested:

-   -   injecting water inside micro-bales. The result is not         satisfactory because of the large density of cotton fibers         inside a micro-bale, which makes the penetration of needles very         difficult and prevents the injected liquid from being uniformly         dispersed inside the micro-bales;     -   spraying water on the cotton fibers; in this alternative, the         micro-bale is opened, a solution is sprayed on the fiber         uniformly, and then the micro-bale is again closed and kept at         room temperature.

The effect of the bacteria belonging to the species Lactobacillus plantarum and Lactobacillus casei rhamnosus on the stickiness of cotton was tested on 50 g cotton micro-bales, as described earlier. The higher the humidity inside the bale, the larger the metabolic activity of the sown bacteria and the faster is the reduction in the stickiness of the thereby treated cotton fibers. It was noticed that, in the case of cotton dried before the treatment according to the invention, the activity of the sown bacteria is reduced.

Preferably, the resulting humidity inside the micro-bale should be between 8 and 13%.

The bacterial treatment of sticky cotton fibers according to the invention does not affect the degree of polymerization of cellulose entering into the composition of the cotton fiber.

Best efficiency was achieved by using a suspension of Lactobacillus plantarum in an amount of 2.5×10⁶ colony-forming units per gram of cotton, for resulting 16% humidity at 21° C. for a week. The results were validated by a conventional adhesiveness test of the treated cotton.

EXAMPLE 3 Application of the Method for Treating Sticky Cotton Fibers on the Scale of a Pilot Station

A pilot test was then conducted, consisting of treating cotton fibers with a high degree of stickiness with bacteria of the genus Lactobacillus plantarum at a concentration of 4×10⁶ colony-forming units per gram of treated cotton, the resulting humidity inside the bale lying between 9.5 and 12%. The thereby treated cotton fibers were then submitted to a standard spinning operation using a speed frame and a ring spinning frame or further to a rotor spinning operation using the centrifugal force principle (machine open end). The obtained results were positive, showing total disappearance of the stickiness of the thereby treated cotton. The quality of the thereby obtained yams is not affected by the treatment.

Complementary tests have shown that addition of 5% humidity does not lead to the occurrence of mold even after one month of incubation at room temperature, which leads to the conclusion that there is no need to arrest growth of microorganisms by subsequent treatment.

EXAMPLE 4 A Method for Industrial Treatment of Sticky Cotton Fibers

The tests for treating sticky cotton on an industrial scale used 6 bales of cotton having 3 stickiness levels as follows:

i. low stickiness: bales S6 and S7;

ii. medium stickiness: bales S8 and S9;

iii. high stickiness: bales S1 and S5.

Both bales having close stickiness levels were mixed before the treatment, the thereby obtained total weight for each stickiness level then being divided into two portions in order to be able to conduct spinning tests with and without bacterial treatments.

Three of the six thereby obtained bales were sown by spraying an aqueous suspension of microorganisms. The suspension was prepared from a freeze-dried powder containing lactic bacteria, notably bacterial belonging to the Lactobacillus plantarum and Lactobacillus casei rhamnosus genera. Said freeze-dried powder is conditioned in bags with a determined weight, for example bags of 100 g. A required and sufficient dose of bacteria for sowing 200 kg of cotton is found in each 100 g bag. The contents of a bag are dissolved in water (100 g of freeze-dried powder for 2 liters of clean water); the powder-water mixture is well stirred. This step is followed by a step for diluting the first obtained suspension in water at room temperature; the volume of added water in this dilution step depends on the weight of sticking cotton to be treated and on the desired humidity. For example, in order to obtain 10% provision of humidity inside a bale of 200 kg, the suspension (2 liters) is diluted into 20 liters of water. The thereby obtained diluted suspension should be sprayed onto the cotton fibers to be treated within a sufficiently short time in order to avoid any reduction in bacterial activity.

The bales are then again closed and weighed in order to accurately determine the amount of water actually added onto the fibers.

The bales are then stored for one week at room temperature.

After control, the added humidity was:

-   -   11% for S1+S5;     -   7.2% for S6+S7;     -   8% for S8+S9, respectively.

A comparison between the qualitative results (measured with an Uster equipment) corresponding to the yarns (NE 30/1) obtained from different bales is shown in Table 1.

The results below show that treatment of sticky cotton fibers according to the invention does not generate any degradation of the quality of the yarn. TABLE 1 S1-S5 S1-S5 S6-S7 S6-S7 S8-S9 S8-S9 with without with without with without treat- treat- treat- treat- treat- treat- ment ment ment ment ment ment USTER combed combed carded carded carded carded Mass CV 13.38 13.42 16.31 16.45 15.82 14.71 (%) Fine 2 4 16 14 10 7 Thick 136 124 406 406 303 174 Neps 370 395 808 792 567 450 Hairiness 5.87 5.74 6.73 6.54 6.48 6.29 Tenacity 14.94 14.15 13.14 12.76 13.50 14.12 (cN/Tex) Elongation 4.35 4.57 3.99 3.70 4.03 3.99 (%)

A fast test for screening the sugar content of the cotton fibers belonging to said bales (according to the Parkins method) was also conducted (Table 2).

These results confirm the positive effect of the treatment on the amount of sugar contained within the sticky cottons. TABLE 2 Sugar Sample Posi- Nega- content N° Sample tive tive (%) Comments 1 S1-S5 with treatment V <0.35 No sugar 2 S1-S5 without treatment V >0.35 Sugars 3 S6-S7 with treatment V <0.35 No sugar 4 S6-S7 without treatment V >0.35 Sugars 5 S8-S9 with treatment V <0.35 No sugar 6 S8-S9 without treatment V >0.35 Sugars 

1. A method for treating sticky cotton fibers intended to reduce the stickiness of said fibers, the method comprising the following steps: a. sowing said cotton fibers with bacteria, by spraying, preferably by uniformly spraying an aqueous suspension of said bacteria, so as to achieve a maximum resulting humidity thereof of 16%; b. storing the thereby treated cotton fibers as a compressed bale; c. letting the sown bacteria act at notably room temperature for at least about one week.
 2. The method according to claim 1, wherein the compressed treated bale is wrapped up and sealed off.
 3. The treatment method according to claim 1, wherein the resulting humidity of the treated cotton bale is at most 13%.
 4. The method according to claim 1, wherein the concentration of bacteria sown inside said bale is at least 105 colony-forming units per gram of cotton.
 5. The method according to claim 1, wherein said aqueous suspension comprises bacteria selected from: Lactobacillus, Pediococcus, Bifidobacterium, Lactococcus, Leuconostoc, Enterococcus and Streptococcus.
 6. The method according to claim 5, wherein the aqueous suspension comprises bacteria belonging to the group: Lactobacillus plantarum and Lactobacillus casei rhamnosus.
 7. The method according to claim 6, wherein the aqueous suspension comprises bacteria belonging to selected strains from Lactobacillus casei rhamnosus R0011 and Lactobacillus plantarum R1012.
 8. The use of a freeze-dried powder containing bacteria selected from: Lactobacillus, Pediococcus, Bifidobacterium, Lactococcus, Leuconostoc, Enterococcus and Streptococcus, for treating sticky cotton fibers.
 9. The use according to claim 8 of a determined amount x of powder contained in a bag for treating an amount y of sticky cotton fibers. 